So, twice over the 2 holiday weeks I have ended up with a dead battery. Second time car sat for 4 days. Thought I had a bad battery in the past so I replaced it like 3 months ago, so know that wasn't the issue. Car jump starts right away and if I let it run for an hr. No issues starting right up the next day so figured there was a short or parasitic draw.

Got a multimeter and disconnected the negative. I tested the battery and that was perfect. I then put the multimeter on 10DC amps and placed it between the negative terminal of the battery and the negative harness to read the draw when the car is off. The display was showing something like .32 and then after a little bit would climb up to around .69 and then would drop down again after a few seconds and then repeat. (Note: not 100% sure how to interpret the numbers cause it looked like it was a dash to the left like a negatibe before showing the DC AMP readings posted). I then starting pulling and replacing interior fuses, one by one, with the door closed (thus not activating/drawing current with anything else). Luckily I started with the bottom row and when I got to the interior light fuse and pulled it the AMPS then dropped to like .06 and held steady. So seems like the issue is on the interior light circuit.

Thinking that I have a bunch of tools and crap in the trunk and that maybe something in there was causing the issue, I opened the pass through to the trunk to make sure that for some reason the trunk light wasn't remaining on or the trunk switch wasn't the source. No light visible through the pass through. What I can tell you is that when the trunk is popped open, the amps jump up, obviously cause the light in the trunk is active, but now the amps hold steady and do not fluctuate. If I close the trunk and turn on lets say the interior light toggle switch, the amps obviously jump up but then jumps up more after a little and back down again, etc like what was happening with everything off. Approx same differential. For good measure I took out the trunk bulb, which had no effect on changing anything when the trunk was closed. I then removed the light harness and that didn;t change anything either. I then removed the harness from the trunk switch. With that eliminated the results were the same as if the trunk was closed and the the .3X reading and then climbing up to .6x after a few seconds and back again, like before. I saw all the wires ran from the trunk switch down the left side of the trunk and removed the liner from inside the trunk and can see no visible damage to anything here. While I thought the tools may have led to an issue with a pinched wire or something the liner keeps everything away from the wiring. Everything looks clean.

So I am thinking in my head that while it seems that the issue is in the trunk, given that when the trunk is open the fluctuation stops and the amps hold steady, It may be that the issue is somewhere else in the circuit and the opening of the trunk levels things out or completes the circuit in a way that there is no issue or maybe ground differential, etc. So what would be my next steps for figuring this out?

 

Have you tried disconnecting the HFL unit and rechecking for a draw? When car is running does the HFL button on steering wheel beep when pressed?

 

I never use the HFL so excuse my ignorance but I'm assuming its the smaller button (set back on steering wheel left side) not the phone buttons (Haven't touched/used those either in years). Yes if you press the one it beeps and then have to press back for it to go back to radio. I read some other posts about people posting that battery draw could be related to HFL. Although many said just taking the module out didn't solve the issue and there is still a draw.

I didn't think it was the case that it could be the HFL since I didn't see that connected on the same circuit in the service manual wiring diagram for interior lights but now see that they don't group things by circuit more by function and HFL seems to be on the same interior fuse (#6) as interior lights. Actually the HFL is on two fuses #6 & #32, it seems. Assuming I am reading this right. Now I have to figure out how to remove it.

 

 

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the crabman beat me to it!

 

Son of a B****. When I did a search about the issue initially I saw all the HFL Module posts and thought that maybe that is my issue. When I pulled the Interior light fuse and searched through the service manual and didn't see the HFL on the interior light schematic I thought it was then something else. Friggin waste of time that was then removing trunk liner etc.

As soon as I posted my reply I saw the instructions in the service manual. Popped it out in about 30 seconds. Once removed (i.e. Step 2 from Justinspace's Post). I then went and checked the battery. When I first hooked up the tester at 10 DC AMPS, It started at around .47 and then in about 3 seconds dropped to .07 and pretty much stayed there. So, this must be the cause.

Justinspace, As far as step 3 are you saying the issue with the control board is a solder issue and can be fixed with heating it up with a heat gun? Or is this require replacing the control module?

Can I remove the module or not hook it up temp? or will this cause other things not to work etc if removed for the interim?

 

Some people have reflowed the solder and added a few months of life to it but ultimately it dies again. You can remove it and not have any issues.

 

Thanks all.

I disconnected it for now and put things back together. Will be away for business next week and car will sit for 4 full days so that will be the test to see if the battery is still alive.